1. Field of the Invention
The invention relates to networks, more particularly to storage area networks (SANs) and yet more particularly to copying data between devices on the SAN.
2. Description of the Related Art
Storage Area Networks (SANs) are becoming more common as a means to lower storage costs and increase storage efficiency while increasing storage flexibility. One common function in an SAN is to copy data from one storage device to another, such as during a backup operation. Conventionally, this is done by the host computer issuing commands to read the data from the original location and write it to the desired location. This method requires extensive use of the host computer. Thus, it is relatively costly in terms of host requirements.
Some parties, such as Crossroads Systems Inc. and Chaparral Network Storage, Inc., provide copy engines which respond to the SCSI Extended Copy Command. Using these engines, the data is transferred directly between the storage devices by this dedicated hardware. Thus host usage is reduced. However, further complexities make such copy engines difficult to use. First, zoning in a SAN is difficult as the copy engine needs access to both devices, even though they would otherwise be in different zones. For more details on zoning, please refer to U.S. patent application Ser. No. 10/123,996 for “FIBRE CHANNEL ZONING BY DEVICE NAME IN HARDWARE” by Ding-Long Wu, David C. Banks and Jieming Zhu Filed Apr. 17, 2002 and Ser. No. 09/426,567 for “METHOD AND SYSTEM FOR CREATING AND IMPLEMENTING ZONES WITHIN A FIBRE CHANNEL SYSTEM,” by David Banks, Kumar Malavalli, Paul Ramsay, Kha Sin Teow, and Jieming Zhu filed Oct. 22, 1999, both of which are hereby incorporated by reference. Further, each host using the copy facility would also have to be zoned to the facility, so this just adds great complexity to zoning schemes and may reduce security in many cases. Further, it is very common for hosts to have different LUN mappings than the internal LUNs on the storage devices. The copy engines do not comprehend these mappings, so each host must be manually configured to understand the various mappings and do conversions when using the copy service. This is a problem for a single host and rapidly becomes unmanageable with multiple hosts.
Thus copying data between storage devices on a SAN has many problems. It would be desirable to provide a simple facility to minimize host usage and administrative burdens such as zoning and LUN mappings.